Coil component and method of manufacturing coil component

ABSTRACT

A coil component includes an annular core and a first coil and a second coil wound around the core. The first coil and the second coil include first wire members and second wire members. The second wire members have end surfaces and which are brought into contact with side surfaces of first and second joining portions at tips of the first wire members. The first wire members and the second wire members are joined to each other with welding portions between the side surfaces of the first and second joining portions at the tips of the first wire members and the end surfaces of the second wire members interposed therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to International PatentApplication No. PCT/JP2017/005010, filed Feb. 10, 2017, and to JapanesePatent Application No. 2016-026150, filed Feb. 15, 2016, the entirecontents of each are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to a coil component and a method ofmanufacturing the coil component.

Background Art

A coil component includes an annular toroidal core and a winding (coil)wound around the toroidal core as described, for example, in JapaneseUnexamined Patent Application Publication No. 11-97249).

SUMMARY

In a coil component in which a large current is required to flow througha winding, it is necessary to wind a thick wire around a toroidal core.Due to the thickness of the wire, a winding bulge occurs. The windingbulge becomes remarkable when using a wire having an outer dimension(diameter) of equal to or more than 1.5 mm In the wound wire, theminimum radius at the inner side of the wire is about 2 times thethickness of the wire. For this reason, for example, in the case ofusing a wire having a diameter of 1.5 mm, the radius at the inner sideof the wire is equal to or more than 3.0 mm Thus, there is a problem inthat the size of coil component becomes larger.

The present disclosure provides a coil component which allows a largecurrent to flow therethrough while being reduced in size and a method ofmanufacturing the coil component.

A method of manufacturing a coil component according to an aspect of thedisclosure includes a first step of arranging a plurality of first wiremembers around an annular core, a second step of arranging second wiremembers between the first wire members adjacent to each other in acircumferential direction of the core and bringing joining surfaces ofthe second wire members into contact with side surfaces of joiningportions at tips of the first wire members, and a third step of forminga coil wound around the core by the first wire members and the secondwire members by welding the side surfaces of the joining portions andthe joining surfaces.

According to this configuration, since the coil is formed by alternatelyjoining the first wire members and the second wire members, windingbulge due to the wires does not occur. Accordingly, it is possible toreduce the size of the coil component which is manufactured using thethick first wire members and second wire members so as to allow a largecurrent to flow therethrough. As a result, it is possible to manufacturethe coil component which is reduced in size and allows a large currentto flow through the coil.

In the above method of manufacturing the coil component, it ispreferable that the first wire members and the second wire members madeof the same metal material be used, and in the third step, the firstwire members and the second wire members be joined together by weldingportions which are formed by melting the first wire members and thesecond wire members.

According to this configuration, the welding portions are made of thesame metal material as that of each of the first wire members and thesecond wire members. Therefore, interfaces, which are easy to begenerated in joining of different types of metals, are difficult to begenerated between the welding portions and the first wire members andbetween the welding portions and the second wire members. Accordingly,it is possible to reduce a resistance value of the coil as compared witha case where the first wire members and the second wire members arejoined together using a joining material such as solder, for example.

In the above method of manufacturing the coil component, it ispreferable that the third step include forming the plurality of weldingportions for joining the side surfaces of the plurality of joiningportions and the plurality of joining surfaces by emission of laserlight, and the plurality of welding portions be formed by the laserlight emitted from the same direction. According to this configuration,since the plurality of welding portions are formed by emitting the laserlight from the same direction, it is possible to perform the process ofjoining the first wire members and the second wire members together in ashort time.

In the above method of manufacturing the coil component, it ispreferable that in the second step, the second wire members berespectively fitted into between the first wire members adjacent to eachother in the circumferential direction of the core to bring the joiningsurfaces of the second wire members into contact with the side surfacesof the joining portions at the tips of the first wire members. Accordingto this configuration, since the joining surfaces of the second wiremembers are fitted with the side surfaces of the joining portions at thetips of the first wire members, gaps are difficult to be generatedbetween the first wire members and the second wire members. Therefore,the joining areas of joint parts when the side surfaces of the joiningportions at the tips of the first wire members and the joining surfacesof the second wire members are welded to each other are increased, andresistance values on the joint parts can be reduced. Note that in thisspecification, fitting refers to tight fitting into a certain form.

In the above method of manufacturing the coil component, it ispreferable that the second wire members having the joining surfacesareas which are larger than average cross-sectional area of the secondwire members be used. According to this configuration, the areas of thejoining surfaces of the second wire members are larger than the averagecross-sectional area of the second wire members. Therefore, it ispossible to increase the contact areas between the side surfaces of thejoining portions at the tips of the first wire members and the joiningsurfaces of the second wire members by the amounts. Accordingly, it ispossible to reduce the resistance values in the joint parts between thefirst wire members and the second wire members. Note that in thisspecification, the average cross-sectional area is a value obtained bydividing a volume of a member by a current path (length).

In the above method of manufacturing the coil component, it ispreferable that the first wire members having step portions formed inthe tips of the first wire members be used, and in the second step, thesecond wire members be fitted into the first wire members so as to abutagainst the step portions. According to this configuration, since thesecond wire members are fitted into the first wire members in a state ofbeing positioned by the step portions, it is possible to suppresspositional deviation when the first wire members and the second wiremembers are joined together.

In the above method of manufacturing the coil component, it ispreferable that the first wire members having the joining portions ofcylindrical shapes be used, and the second wire members having thejoining surfaces as recessed cylindrical surfaces which are provided onend portions of the second wire members and are fitted with the joiningportions be used. In addition, in the above method of manufacturing thecoil component, it is preferable that the first wire members having thejoining portions of cylindrical shapes be used, and the second wiremembers having the joining surfaces as inner circumferential surfaces ofthrough-holes which are provided in the second wire members and intowhich the joining portions are tightly fitted be used.

According to these configurations, even if the angles formed between thefirst wire members and the second wire members, that is, the positionsof the second wire members around the axial lines of the joiningportions of the first wire members are changed, the contact areasbetween the side surfaces of the joining portions and the joiningsurfaces are not changed or are slightly changed even when the contactareas are changed. Therefore, the degree of freedom in the arrangementof the first wire members and the second wire members is increased.Accordingly, even if there are variations in the positional relationshipbetween the second wire members and the first wire members which arefitted with the second wire members, it is possible to suppress decreasein the contact areas due to such variations and eventually increase inthe joint resistances between both of the wire members.

In the above method of manufacturing the coil component, it ispreferable that wire members having rectangular cross sections be usedas at least one of the first wire members and the second wire members.According to this configuration, for example, when the wire members areplaced on, for example, a jig or when the wire members are placed atpredetermined positions using a supply device, the postures of the wiremembers are difficult to be changed and thus it is easy to maintain theplaced states.

A coil component according to another aspect of the disclosure includesan annular core, and a coil wound around the core, wherein the coilincludes a plurality of first wire members and a plurality of secondwire members, the second wire members have joining surfaces in contactwith side surfaces of joining portions at tips of the first wiremembers, and the first wire members and the second wire members arejoined together with welding portions between the side surfaces of thejoining portions and the joining surfaces interposed therebetween.According to this configuration, since the coil is formed by alternatelyjoining the first wire members and the second wire members, the windingbulge due to the wires does not occur. Accordingly, it is possible toreduce the size of the coil component using the thick first wire membersand second wire members so as to allow a large current to flowtherethrough. As a result, the coil component allows a large current toflow through the coil while being reduced in size.

In the above coil component, it is preferable that areas of the joiningsurfaces be larger than the average cross-sectional area of the secondwire members. According to this configuration, the areas of the joiningsurfaces of the second wire members are larger than the averagecross-sectional area of the second wire members. Therefore, it ispossible to increase the contact areas between the side surfaces of thejoining portions at the tips of the first wire members and the joiningsurfaces of the second wire members by the amounts. Accordingly, it ispossible to reduce the resistance values in the joint parts between thefirst wire members and the second wire members.

In the above coil component, it is preferable that the first wiremembers, the second wire members, and the welding portions be made ofthe same metal material. According to this configuration, the weldingportions are made of the same metal material as that of each of thefirst wire members and the second wire members. Therefore, interfaces,which are easy to be generated in joining of different types of metals,are difficult to be generated between the welding portions and the firstwire members and between the welding portions and the second wiremembers. Accordingly, it is possible to reduce the resistance value ofthe coil as compared with a case where the first wire members and thesecond wire members are joined together using a joining material such assolder, for example.

In the above coil component, it is preferable that the joining portionshave cylindrical shapes and the joining surfaces be recessed cylindricalsurfaces which are provided in end portions of the second wire membersand are fitted with the joining portions. In addition, in the above coilcomponent, it is preferable that the joining portions have cylindricalshapes, and the joining surfaces be inner circumferential surfaces ofthrough-holes which are provided in end portions of the second wiremembers and into which the joining portions are tightly fitted.

According to these configurations, even if the angles formed between thefirst wire members and the second wire members, that is, the positionsof the second wire members around the axial lines of the joiningportions of the first wire members are changed, the contact areasbetween the side surfaces of the joining portions and the joiningsurfaces are not changed or are slightly changed even when the contactareas are changed. Therefore, the degree of freedom in the arrangementof the first wire members and the second wire members is increased.Accordingly, even if there are variations in the positional relationshipbetween the second wire members and the first wire members which arefitted with the second wire members, it is possible to suppress decreasein the contact areas due to such variations and eventually increase inthe joint resistances between both of the wire members.

In the above coil component, it is preferable that at least one of thefirst wire members and the second wire members have square crosssections. According to this configuration, it is possible to reduce theresistance values of the wire members having the square cross sectionsas compared with a case of using wire members having the same outerdimensions and circular cross sections. In addition, as compared with acase of using wire members having the same cross-sectional areas and thecircular cross sections, the outer dimensions become smaller and thesize of the coil can be reduced.

In the above coil component, it is preferable that at least one of thefirst wire members and the second wire members have circular crosssections. In general, the wire members having the circular crosssections are preferably used in order to reduce the cost of the coilcomponent because the wire members having the circular cross sectionsare more inexpensive than wire members having rectangular crosssections.

According to the coil component and the method of manufacturing the coilcomponent in the disclosure, a large current can be made to flow throughthe coil component while the coil component is made small in size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a first embodiment of a coilcomponent;

FIG. 2 is a schematic bottom view showing the first embodiment of thecoil component;

FIG. 3 is an exploded perspective view showing the first embodiment ofthe coil component;

FIG. 4A is a perspective view showing a core and first and second wiremembers, and FIG. 4B is an enlarged perspective view of the first andsecond wire members;

FIGS. 5A to 5C are descriptive views for explaining a method ofmanufacturing the coil component;

FIGS. 6A to 6C are descriptive views for explaining the method ofmanufacturing the coil component;

FIG. 7 is a descriptive view for explaining the method of manufacturingthe coil component;

FIG. 8 is a descriptive view for explaining the method of manufacturingthe coil component;

FIG. 9 is a descriptive view for explaining the method of manufacturingthe coil component;

FIG. 10 is a descriptive view for explaining the method of manufacturingthe coil component;

FIG. 11 is a descriptive view for explaining the method of manufacturingthe coil component;

FIG. 12 is a perspective view showing a second embodiment of a coilcomponent;

FIG. 13 is an exploded perspective view showing the second embodiment ofthe coil component;

FIG. 14 is a plan view showing the second embodiment of the coilcomponent;

FIG. 15 is a perspective view showing a third embodiment of a coilcomponent;

FIG. 16 is an exploded perspective view showing the third embodiment ofthe coil component;

FIG. 17 is a plan view showing the third embodiment of the coilcomponent;

FIG. 18 is a perspective view showing a core and first and secondmembers in the third embodiment; and

FIGS. 19A to 19D are partial perspective views of first and secondmembers of another embodiment.

DETAILED DESCRIPTION

Hereinafter, respective modes will be described. It should be noted thatthe accompanying drawings illustrate components in an enlarged mannerfor facilitating understanding. Dimensional ratios of the components maybe different from actual ratios or ratios in different drawings.

First Embodiment

Hereinafter, a first embodiment will be described.

As shown in FIG. 1 and FIG. 2, a coil component 1 includes a core 30, afirst coil 40A, a second coil 40B, a rectangular parallelepiped case 10,and first to fourth electrode terminals 21 to 24 attached to the case10. The case 10 has a box body 11 having an opening and a lid body 12attached to the opening of the box body 11. The case 10 is made of, forexample, resin such as polyphenylene sulfide resin or ceramics.

The first to fourth electrode terminals 21 to 24 are attached to thelower surface of a bottom portion 13 of the box body 11. The first tofourth electrode terminals 21 to 24 are formed by plate members and haveshapes bent from the lower surface of the bottom portion 13 toward theside surfaces. The first to fourth electrode terminals 21 to 24 aredisposed at four corners of the bottom portion 13. Further, the bottomportion 13 has a pair of openings 14 which are adjacent to each otherwith a central portion thereof interposed therebetween. Parts of thefirst to fourth electrode terminals 21 to 24 are exposed to the insideof the box body 11 through the pair of openings 14.

As shown in FIG. 2, the core 30, the first coil 40A, and the second coil40B are accommodated in the case 10. FIG. 2 is a view of the case 10 asviewed from the lower surface side of the bottom portion 13 of the boxbody 11, and the first to fourth electrode terminals 21 to 24 areindicated by two-dot chain lines.

As shown in FIG. 3, the core 30 is, for example, an annular magneticcore (toroidal core) having an annular shape. The surface (also referredto as a longitudinal cross section) of the core 30 cut in a planeperpendicular to the circumferential direction of the core 30 has arectangular shape.

As shown in FIG. 4A, the core 30 has a first end surface 30 a and asecond end surface 30 b that have a front-rear relationship in the axialdirection. Further, the core 30 has an inner side surface 30 c at theinner side in the radial direction and an outer side surface 30 d at theouter side in the radial direction. The first end surface 30 a of thecore 30 faces the bottom portion 13 of the box body 11 shown in FIG. 3.The second end surface 30 b of the core 30 faces the lid body 12 shownin FIG. 3.

The core 30 is made of, for example, a metal-based material such as softferrite and iron or a metal magnetic material. When the metal-basedmaterial is used, it is preferable to form an insulating film bysticking an insulating sheet on the surface or applying an insulatingagent thereto.

The first coil 40A and the second coil 40B are wound around the core 30.As shown in FIG. 2, a first end portion 401 a of the first coil 40A iselectrically connected to the part of the first electrode terminal 21,which is exposed to the inside of the box body 11 through the opening 14thereof. Similarly, a second end portion 402 a of the first coil 40A iselectrically connected to the second electrode terminal 22. A first endportion 401 b of the second coil 40B is electrically connected to thethird electrode terminal 23 and a second end portion 402 b of the secondcoil 40B is electrically connected to the fourth electrode terminal 24.

The winding direction of the first coil 40A around the core 30 isopposite to the winding direction of the second coil 40B around the core30. The number of turns of the first coil 40A is equal to that of thesecond coil 40B. The first coil 40A and the second coil 40B are used as,for example, a primary coil, a secondary coil, and a common mode chokecoil.

The first coil 40A and the second coil 40B will now be described. Asshown in FIG. 4A, the first coil 40A and the second coil 40B include aplurality of first wire members 41 and a plurality of second wiremembers 42. The plurality of first and second wire members 41 and 42 arejoined together. The first and second wire members 41 and 42 arealternately joined together. In other words, in the pair of first wiremembers 41 and 41 adjacent to each other in the circumferentialdirection of the core 30, an end portion of one first wire member 41 inan outer side portion in the radial direction of the core 30 isconnected to one end portion of the second wire member 42, and the otherend portion of the second wire member 42 is connected to an end portionof the other wire member 41 in an inner side portion in the radialdirection of the core 30. By repeating this joint, the first coil 40Aand the second coil 40B are spirally wound around the core 30.

The first wire members 41 and the second wire members 42 have differentshapes. The first wire members 41 are substantially U-shaped wires. Thesecond wire members 42 are substantially linear wires. Here, the“substantially U shape” includes a U shape, a semicircular shape, andthe like. The substantially linear shape includes a linear shape or ashape having a slight bend or curve. With these shapes, a unit elementof one turn is formed by one first wire member 41 and one second wiremember 42.

The first wire members 41 are arranged so as to surround the inner sidesurface 30 c, the outer side surface 30 d, and the second end surface 30b of the core 30. The second wire members 42 are arranged so as to facethe first end surface 30 a of the core 30. Further, the second wiremembers 42 are arranged between the tips of the two adjacent first wiremembers 41. The first and second wire members 41 and 42 are alignedalong the circumferential direction of the first coil 40A and the secondcoil 40B.

The first wire members 41 adjacent to each other in the circumferentialdirection of the core 30 are spaced apart from each other. Similarly,the second wire members 42 adjacent to each other in the circumferentialdirection of the core 30 are spaced apart from each other. Thus, unlikea case where gaps between the first wire members 41 and between thesecond wire members 42 are filled with a filling material such as resin,it is possible to reduce stress on the core 30 by the filling materialto reduce magnetostriction.

When the first and second wire members 41 and 42 are covered with theinsulating film, the gaps between the first wire members 41 and betweenthe second wire members 42 may be filled with a dielectric material. Thedielectric material is, for example, resin containing a metal filler(such as copper (Cu) or silver (Ag)). Thus, it is possible to preventdecrease in magnetic force due to the dielectric material.

The first and second wire members 41 and 42 are made of, for example, aconductive material such as pure copper (Cu). Note that for the firstand second wire members 41 and 42, a commonly-employed metal material,for example, gold (Au), silver (Ag), or aluminum (Al) may be used.Alternatively, a material obtained by plating copper (Cu) with nickel(Ni) or the like may be used.

The first and second wire members 41 and 42 are joined together bywelding. In this embodiment, welding portions 45 formed by melting thefirst and second wire members 41 and 42 are formed between the members.In FIG. 3 and FIG. 4A, some welding portions 45 of the first and secondwire members 41 and 42 are shown and the others are omitted to show theshapes of the wire members.

The welding portions 45 are formed by, for example, laser beam welding.For example, a YAG laser, a fiber laser, or the like is used for thelaser beam welding. By partially melting the first wire members 41 andthe second wire members 42 by emitting the laser light thereto, thefirst wire members 41 and the second wire members 42 are joinedtogether. The first wire members 41 and the second wire members 42 thusjoined together and the welding portions 45 thereof contain only thematerial of the first wire members 41 and the second wire members 42,and do not contain a joining material such as solder. In other words,the first wire members 41 and the second wire members 42 are joinedtogether to form the first coil 40A and the second coil 40B. When thetwo wire members are joined together using the joining material, thejoining material creates two interfaces with different materials betweenthe two wire members. The resistance values of the coils composed of thetwo wire members and the joining material are increased due to thepresence of the interfaces.

On the other hand, as described above, the first coil 40A in theembodiment includes the first wire members 41 and the second wiremembers 42 and does not include the joining material. Therefore, theresistance value of the first coil 40A is smaller than that of the coilusing the joining material. The second coil 40B is also similar to thefirst coil 40A. Accordingly, the first wire members 41 and the secondwire members 42 are melted by the laser beam welding and joined togetherto form the first coil 40A and the second coil 40B, thereby suppressingincrease in the resistance value.

The first wire members 41 and the second wire members 42 will now bedescribed in detail. FIG. 4B shows two adjacent first wire members 41and 41 and one second wire member 42 to be connected therebetween. Notethat in FIG. 4B, when the two first wire members 41 and 41 aredistinguished from each other, they will be described as first wiremembers 41X and 41Y.

Each first wire member 41 has first and second columnar portions 41 aand 41 b and a connecting portion 41 c which connects one ends (baseends) of the first and second columnar portions 41 a and 41 b to eachother. The first and second columnar portions 41 a and 41 b and theconnecting portion 41 c have square cross sections and are formedsubstantially linearly. The outer dimensions of the first and secondcolumnar portions 41 a and 41 b and the connecting portion 41 c, i.e.,the thicknesses (the lengths of one sides of the cross sections) thereofare, for example, 1.5 mm

A first joining portion 41 d is formed at the tip of the first columnarportion 41 a. The first joining portion 41 d is formed in a cylindricalshape. For example, the outer dimension of the first joining portion 41d, i.e., the diameter thereof is, for example, 1.5 mm, and is equal tothe thickness of the first columnar portion 41 a. As described above, byforming the first joining portion 41 d in the cylindrical shape for theprismatic first columnar portion 41 a, the four corners of the firstcolumnar portion 41 a protrude outward relative to the side surface ofthe first joining portion 41 d when viewed from the tip side, that is,from the side of the first joining portion 41 d. These protrudingportions are referred to as a step portion 41 e. Similarly to the firstcolumnar portion 41 a, a second joining portion 41 f is formed at thetip of the second columnar portion 41 b. In addition, four cornerportions of the second columnar portion 41 b, which protrude outwardrelative to the side surface of the second joining portion 41 f whenviewed from the tip side, that is, from the side of the second joiningportion 41 f are referred to as a step portion 41 g.

The first columnar portion 41 a is disposed in an outer side portion inthe radial direction of the core 30 shown in FIG. 4A, and the secondcolumnar portion 41 b is arranged in an inner side portion in the radialdirection of the core 30. Accordingly, the first columnar portion 41 aand the second columnar portion 41 b are arranged with the core 30interposed therebetween. The first columnar portion 41 a and the secondcolumnar portion 41 b are arranged so as to extend along the centralaxis of the core 30. The connecting portion 41 c is arranged at the sideof the second end surface 30 b of the core 30. The first joining portion41 d at the tip of the first columnar portion 41 a and the secondjoining portion 41 f at the tip of the second columnar portion 41 bproject to the side of the first end surface 30 a of the core 30.

The second wire member 42 has a square cross section. The thickness ofthe second wire member 42 is equal to the heights of the first andsecond joining portions 41 d and 41 f of the first wire member 41, andis, for example, 1.5 mm As shown by two-dot chain lines in FIG. 4B, thesecond wire member 42 is arranged between the tips of the first wiremembers 41X and 41Y arranged adjacent to each other.

The first joining portions 41 d formed at the tips of the first wiremembers 41X and 41Y are arranged in the outer side portions in theradial direction of the core 30 shown in FIG. 4A, and the second joiningportions 41 f formed at the tips of the first wire members 41X and 41Yare arranged in the inner side portions in the radial direction of thecore 30. The second wire member 42 is arranged between the secondjoining portion 41 f formed at the tip of the second columnar portion 41b of the first wire member 41X and the first joining portion 41 d formedat the tip of the first columnar portion 41 a of the first wire member41Y in the adjacently arranged first wire members 41X and 41Y.

An end surface 42 a of the second wire member 42 abuts against the sidesurface of the second joining portion 41 f of the first wire member 41X.The end surface 42 a serves as a joining surface which joins the secondwire member 42 to the side surface of the second joining portion 41 f ofthe first wire member 41. An end surface 42 b of the second wire member42 abuts against the side surface of the first joining portion 41 d ofthe first wire member 41Y. The end surface 42 b serves as a joiningsurface which joins the second wire member 42 to the side surface of thefirst joining portion 41 d of the first wire member 41. The end surfaces42 a and 42 b of the second wire member 42 are formed so as to haveareas larger than an average cross-sectional area of the second wiremember 42 (an average cross-sectional area of a cross section in aquadrangular columnar portion). The average cross-sectional area is avalue obtained by dividing the volume of the member by a current path(length).

Further, the end surfaces 42 a and 42 b of the second wire member 42 andthe side surfaces of the first and second joining portions 41 d and 41 fof the first wire members 41 (41X and 41Y) are formed so as to be fittedwith each other. In other words, the end surfaces 42 a and 42 b of thesecond wire member 42 are formed in shapes following the side surfacesof the first and second joining portions 41 d and 41 f of the first wiremembers 41 (41X and 41Y) (such that the shapes of the respectivesurfaces which are in contact with each other in fitting are the same).In this way, portions where the shapes of the two portions correspond toand make plane contact with each other are referred to as fitting parts.Such fitting parts facilitate the joining of the first wire members 41and the second wire members 42.

Specifically, the end surfaces 42 a and 42 b of the second wire member42 are recessed cylindrical surfaces that are fitted with the sidesurfaces of the first and second cylindrical joining portions 41 d and41 f and have the same curvatures as those of the side surfaces. Itshould be noted that the length of each recessed cylindrical surface inthe circumferential direction is equal to the length of the halfcircumference of each of the first and second joining portions 41 d and41 f.

Next, a method of manufacturing the above-described coil component 1will be described. As shown in FIG. 5A, the first wire members 41 arealigned using a jig 100. Each first wire member 41 is formed by bendinga linear bar material having a square cross section and processing thetips thereof into cylindrical shapes. Each second wire member 42 isformed by processing end portions of a linear bar material having asquare cross section into the recessed cylindrical end surfaces 42 a and42 b. Insertion holes 100 a and 100 b for inserting the first and secondcolumnar portions 41 a and 41 b of the first wire members 41 thereintoare formed in the jig 100.

As shown in FIG. 5B, an adhesive jig 101 is attached to the first wiremembers 41 inserted into the jig 100. For example, the adhesive jig 101is formed by applying an adhesive material to the surface of a resinfilm such as PET or the like. Note that a rubber sheet may be used asthe adhesive jig 101.

As shown in FIG. 5C, after detaching the first wire members 41 from thejig 100 (see FIG. 5B), they are arranged while the adhesive jig 101 isat the lower side. Thus, the plurality of first wire members 41 aretemporarily fixed to the upper surface of the adhesive jig 101. At thistime, the plurality of first wire members 41 are arranged such that thefirst and second joining portions 41 d and 41 f at the tips of the firstwire members 41 face upward.

As shown in FIG. 6A, the second wire members 42 are aligned using a jig110. Positioning projections 110 a are formed on the upper surface ofthe jig 110. The second wire members 42 are placed on the upper surfaceof the jig 110 so as to correspond to these projections 110 a. Thesecond wire members 42 are formed in prismatic shapes (having squarecross sections). Therefore, each of the second wire members 42 can beeasily aligned such that axial lines of the end surfaces 42 a and 42 bwhich are the recessed cylindrical surfaces of the second wire member 42(see dashed lines in FIG. 6A) are perpendicular to the upper surface ofthe jig 110. Further, since the second wire members 42 have theprismatic shapes, an aligned state is maintained.

As shown in FIG. 6B, an adhesive jig 111 is made to adhere to the secondwire members 42 aligned on the jig 110. For example, the adhesive jig111 is formed by applying an adhesive material to the surface of a resinfilm such as PET or the like. Note that a rubber sheet may be used asthe adhesive jig 111.

As shown in FIG. 6C, after detaching the second wire members 42 from thejig 110 (see FIG. 6B), they are arranged while the adhesive jig 111 isat the lower side. Thus, the plurality of second wire members 42 aretemporarily fixed to the upper surface of the adhesive jig 111.

As shown in FIG. 7, the core 30 is inserted between the first and secondcolumnar portions 41 a and 41 b of the plurality of first wire members41 temporarily fixed to the upper surface of the adhesive jig 101.Through the above steps, the plurality of first wire members 41 arearranged around the core 30.

As shown in FIG. 8, the second wire members 42 temporarily fixed to theadhesive jig 111 are inserted between the first wire members 41, and thesecond wire members 42 are fitted into the first wire members 41. Inother words, the side surfaces of the first and second joining portions41 d and 41 f of the first wire members 41 are made to face the endsurfaces 42 a and 42 b of the second wire members 42. Then, for example,as indicated by an arrow in FIG. 8, the adhesive jig 111 is moved in thehorizontal direction. Since the second wire members 42 are insertedbetween the tips of the first wire members 41, only the adhesive jig 111is moved and the second wire members 42 are detached from the adhesivejig 111. At this time, end portions of the second wire members 42 abutagainst the step portions 41 e and 41 g of the first wire members 41,and the second wire members 42 are positioned in a state of being fittedinto the first wire members 41.

As shown in FIG. 9, laser light is emitted to the fitting parts of thefirst wire members 41 and the second wire members 42 from the samedirection, specifically, from the upper side so as to be incidentthereon in parallel with the axial lines of the first and second joiningportions 41 d and 41 f of the first wire members 41. The side surfacesof the first and second joining portions 41 d and 41 f of the first wiremembers 41 are thereby welded to the end surfaces 42 a and 42 b of thesecond wire members 42. Arrows in FIG. 9 indicate emitting positions ofthe laser light. The emitting positions of the laser light are thefitting parts between the side surfaces of the first and second joiningportions 41 d and 41 f of the first wire members 41 and the end surfaces42 a and 42 b of the second wire members 42.

When a laser device having a large laser irradiation area (spotdiameter) and a high peak irradiation energy is used as a device foremitting the laser light, for example, a YAG laser is used, the laserlight is emitted to spots on the fitting parts. As the YAG laser, forexample, a laser device having a peak energy of 7 kW, an irradiationtime of 10 ms, an irradiation energy of 70 J, a spot diameter of 0 5 mm,and a power density of about 350 W/cm² can be used. The first wiremembers 41 and the second wire members are melted by the laser light,and the welding portions 45 shown in FIG. 3 and FIG. 4A are formed byhardening. Then, the first wire members 41 and the second wire members42 are joined together to form the first coil 40A and the second coil40B shown in FIG. 4A.

When a laser device having a small laser irradiation area (spotdiameter) and a low peak irradiation energy is used as the device foremitting the laser light, for example, a fiber laser is used, the laserlight is continuously emitted along the above-described fitting parts.As the fiber laser, for example, a laser device having a peak energy of1 kW, an irradiation time of 200 ms, an irradiation energy of 200 J, aspot diameter of 0.04 mm, and a power density of about 8000 W/cm² can beused. In this case, the welding portions 45 are formed so as to extendalong the first and second joining portions 41 d and 41 f of the firstwire members 41 and the end surfaces 42 a and 42 b of the second wiremembers 42. As described above, since the irradiation positions of thelaser light having the small irradiation area can be focused on, theirradiation positions can be controlled with high accuracy. Therefore,it is possible to reduce reflection and emission of the laser light toother portions.

In addition, since the fitting parts of the side surfaces of the firstand second joining portions 41 d and 41 f of the first wire members 41and the end surfaces 42 a and 42 b of the second wire members 42 are allexposed upward, the laser light can be emitted to the respective fittingparts in the same direction.

As shown in FIG. 10, the first coil 40A, the second coil 40B, and thecore 30 are inserted into the box body 11 to which the first to fourthelectrode terminals 21 to 24 have been attached. Then, the first coil40A and the first and second electrode terminals 21 and 22 areelectrically connected to each other, and the second coil 40B and thethird and fourth electrode terminals 23 and 24 are electricallyconnected to each other. For example, by the laser beam welding, thefirst and second end portions 401 a, 402 a, 401 b, and 402 b of thefirst coil 40A and the second coil 40B are respectively welded to thefirst to fourth electrode terminals 21 to 24. Note that the first andsecond end portions 401 a, 402 a, 401 b, and 402 b of the first coil 40Aand the second coil 40B may be respectively joined to the first tofourth electrode terminals 21 to 24 using the joining material such assolder.

As shown in FIG. 11, the lid body 12 is attached to the opening of thebox body 11. The lid body 12 is fixed to the box body 11 by, forexample, an adhesive. Note that the lid body 12 may be fixed to the boxbody 11 by fitting.

As described above, according to the embodiment, the followingoperational effects can be obtained.

(1-1) Since the first coil 40A and the second coil 40B are formed byalternately joining the first wire members 41 and the second wiremembers 42 together, winding bulge due to the wires does not occur.Accordingly, it is possible to reduce the size of the coil component 1.Further, the end surfaces 42 a and 42 b of the second wire members 42are fitted with the side surfaces of the first and second joiningportions 41 d and 41 f at the tips of the first wire members 41. Inother words, the side surfaces of the first and second joining portions41 d and 41 f come into contact with the end surfaces 42 a and 42 b ofthe second wire members 42 with shapes that follow each other. Gaps aretherefore difficult to be generated between the first wire members 41and the second wire members 42. Therefore, when the side surfaces of thefirst and second joining portions 41 d and 41 f of the first wiremembers 41 and the end surfaces 42 a and 42 b of the second wire members42 are joined together, heat of the laser light is easily transferred.Accordingly, it is possible to increase the joining areas of the jointparts, i.e., the cross sections of the welding portions 45. As a result,the resistance values on the joint parts become small, and a largecurrent can be made to flow through the first coil 40A and the secondcoil 40B. Further, the resistance values are reduced and heat generationdue to the current is suppressed, thereby increasing the amount ofcurrent flowing through the first coil 40A and the second coil 40B. Forexample, a coil component of a class 15 A can be changed to that of aclass 20 A. In addition, since heat is easily transmitted, it ispossible to join them in a short time with the laser light of constantoutput and a processing speed can be increased. On the other hand,preferable joint can be achieved even when laser light of low output isused.

(1-2) Since the areas of the end surfaces 42 a and 42 b of the secondwire members 42 are larger than the average cross-sectional area of thesecond wire members 42, it is possible to increase the contact areasbetween the side surfaces of the first and second joining portions 41 dand 41 f at the tips of the first wire members 41 and the end surfaces42 a and 42 b of the second wire members 42 by the amounts. Accordinglyit is possible to reduce the resistance values in the joint partsbetween the first wire members 41 and the second wire members 42.

In the manufacturing process, compared with the case where thecross-sectional areas of the second wire members 42 are made equal tothe average cross-sectional area, the welding areas of the weldingportions 45 are easily made larger than the average cross-sectionalarea, and thus the joining strength at the joint parts is easilyincreased. When it is sufficient that minimum welding areas equal to theaverage cross-sectional area of the second wire members 42 can beensured, it is possible to form the welding portions 45 withoutperforming the positioning of a machine which is used for joining (forexample, adjusting the irradiation positions of the laser light in thelaser device) with high accuracy. Thus, it is possible to shorten a timerequired for the joining process.

(1-3) The welding portions 45 are made of the same metal material as thefirst wire members 41 and the second wire members 42. Therefore,interfaces, which are easy to be generated in joining of different typesof metals, are made difficult to be generated between the weldingportions 45 and the first wire members 41 and between the weldingportions 45 and the second wire members 42. Accordingly, it is possibleto reduce the resistance values of the first coil 40A and the secondcoil 40B as compared with a case where the first wire members 41 and thesecond wire members 42 are joined together using the joining materialsuch as solder, for example.

(1-4) The first and second joining portions 41 d and 41 f at the tips ofthe first wire members 41 have the cylindrical shapes, and the endsurfaces 42 a and 42 b of the second wire members 42 are the recessedcylindrical surfaces having the curvatures equal to those of the firstand second joining portions 41 d and 41 f. Accordingly, even if theangles formed between the first wire members 41 and the second wiremembers 42, that is, the positions of the second wire members 42 aroundthe axial lines of the first and second joining portions 41 d and 41 fof the first wire members 41 are changed, the contact areas between theside surfaces of the first and second joining portions 41 d and 41 f andthe end surfaces 42 a and 42 b of the second wire members 42 are notchanged or are slightly changed even when the contact areas are changed.Therefore, the degree of freedom in the arrangement of the first andsecond wire members 41 and 42 is increased. Accordingly, even if thereare variations in the positional relationship between the second wiremembers 42 and the first wire members 41 which are fitted with thesecond wire members 42, it is possible to suppress the increase in thejoint resistances between both of the wire members 41 and 42 due to suchvariations. Further, during welding, positional deviation of the firstwire members 41 and the second wire members 42 hardly occurs, so thatoccurrence of welding failure can be suppressed and a yield can beimproved.

(1-5) The first wire members 41 and the second wire members 42 are thebar materials (square materials, square wires) having the square crosssections. Therefore, when the first and second wire members 41 and 42are respectively placed on the jigs 100 and 110 and the adhesive jigs101 and 111, the postures of the respective first and second wiremembers 41 and 42 are hard to be changed, and thus it is easy tomaintain the placed states.

(1-6) Since the first and second wire members 41 and 42 have the squarecross sections, it is possible to reduce the resistance values of thefirst and second wire members 41 and 42 as compared with a case of usingwire members having the same outer dimensions and circular crosssections. Further, as compared with a case where wire members having thecircular cross sections and the cross-sectional areas of which are equalto those of the first and the second wire members 41 and 42 areemployed, the outer dimensions of the wire members are reduced and thesizes of the first coil 40A and the second coil 40B can be reduced.

(1-7) The fitting parts of the side surfaces of the first and secondjoining portions 41 d and 41 f of the first wire members 41 and the endsurfaces 42 a and 42 b of the second wire members 42 are all exposedupward. Therefore, it is possible to emit the laser light to theplurality of fitting parts from the same direction, and it is notnecessary to change the postures of the first wire members 41 and thesecond wire members 42 with respect to the laser device that emits thelaser light, or the change amounts are small even if the postures arechanged. Thus, the welding process can be completed in a short time. Inaddition, since the welding portions 45 can be seen from one direction,it is possible to easily check the welding portions 45 in which weldingfailure has occurred.

(1-8) Since the second wire members 42 are fitted into the first wiremembers 41 in a state of being positioned by the step portions 41 e and41 g of the first wire members 41, positional deviation is unlikely tooccur during welding, and a time taken for the welding process can beshortened.

(1-9) The heights of the first and second joining portions 41 d and 41 fof the first wire members 41 are equal to the thicknesses of the secondwire members 42. Accordingly, the upper surfaces of the second wiremembers 42 positioned by the step portions 41 e and 41 g flush with theend surfaces (upper surfaces) of the first and second joining portions41 d and 41 f. Thus, it is possible to easily control focusing of thelaser light on both of the upper surfaces of the first and secondjoining portions 41 d and 41 f of the first wire member 41 and the uppersurfaces of the second wire members 42.

Second Embodiment

Hereinafter, a second embodiment will be described.

In this embodiment, the same constituent members as those in theabove-described first embodiment will be denoted by the same referencesigns, and description thereof will be appropriately omitted. Further,description of relationships between the same constituent members willbe also appropriately omitted.

As shown in FIG. 12 and FIG. 13, a coil component la includes the core30, a first coil 40C, a second coil 40D, a rectangular parallelepipedcase 10 a, and first to fourth electrode terminals 21 a to 24 a attachedto the case 10 a. The case 10 a has a box body 11 a having an openingand a lid body 12 a attached to the opening of the box body 11 a. Thecase 10 a is made of, for example, resin such as polyphenylene sulfideresin or ceramics. The first to fourth electrode terminals 21 a to 24 aare attached to the lower surface of a bottom portion 13 a of the boxbody 11 a.

As shown in FIGS. 13 and 14, the core 30, the first coil 40C, and thesecond coil 40D are accommodated in the case 10 a. The first coil 40Cand the second coil 40D are wound around the core 30. The first coil 40Cincludes the plurality of first wire members 41 and second wire members42, two third wire members 431 a and 432 a, and two electrode wiremembers 441 a and 442 a. The second coil 40D includes the plurality offirst wire members 41 and second wire members 42, two third wire members43 lb and 432 b, and two electrode wires 441 b and 442 b.

As shown in FIG. 13, the electrode wire members 441 a, 442 a, 441 b, and442 b stand on the upper surface of the bottom portion 13 of the boxbody 11 a. The electrode wire members 441 a, 442 a, 441 b, and 442 b areembedded in the bottom of the case 10 a until positions where parts oflower end portions thereof respectively come into contact with the firstto fourth electrode terminals 21 a, 22 a, 23 a, and 24 a. The electrodewire members 441 a, 442 a, 441 b, and 442 b are connected to the firstto fourth electrode terminals 21 a, 22 a, 23 a, and 24 a, respectively,mechanically by crimping or the like or electrically by a joiningmaterial. Similarly to the first wire members 41, joining portions 443are formed at the tips of the electrode wire members 441 a, 442 a, 441b, and 442 b.

In the first coil 40C, the third wire member 431 a is arranged betweenthe first wire member 41 and the electrode wire member 441 a. Therespective end surfaces of the third wire member 431 a are recessedcylindrical surfaces similar to those of the second wire members 42. Oneend surface of the third wire member 431 a is joined to the firstjoining portion 41 d of the first wire member 41 by welding, and theother end surface thereof is joined to the joining portion 443 of theelectrode wire member 441 a by welding. Similarly, the third wire member432 a is arranged between the first wire member 41 and the electrodewire member 442 a. The third wire member 432 a has the same shape asthat of the third wire member 431 a, and the end surfaces thereof arerespectively joined to the second joining portion 41 f of the first wiremember 41 and the joining portion 443 of the electrode wire member 442 aby welding.

The second coil 40D is configured similarly to the first coil 40C. Thethird wire member 431 b is arranged between the first wire member 41 andthe electrode wire member 441 b. Similarly to the third wire member 431a, the respective end surfaces of the third wire member 431 b are asrecessed cylindrical surfaces. One end surface of the third wire member431 b is joined to the first joining portion 41 d of the first wiremember 41 by welding, and the other end surface thereof is joined to thejoining portion 443 of the electrode wire member 441 b by welding.Similarly, the third wire member 432 b is arranged between the firstwire member 41 and the electrode wire member 442 b. The third wiremember 432 b has the same shape as that of the third wire member 431 b,and the end surfaces thereof are respectively joined to the secondjoining portion 41 f of the first wire member 41 and 443 of theelectrode wire member 442 b by welding.

The third wire members 431 a, 432 a, 431 b, and 432 b in states of beingaccommodated in the box body 11 a are joined to the first wire members41, and the electrode wire members 441 a, 442 a, 441 b, and 442 b byemitting the laser light from the same direction in the same way as thesecond wire members 42 in the welding step shown in FIG. 9, for example.In other words, the welding process of the third wire members 431 a, 432a, 431 b, and 432 b and the other components can be performedcontinuously to the welding process of the second wire members 42 andthe other components.

As described above, according to the embodiment, in addition to the sameoperational effects as those in the above-described first embodiment,the following operational effects can be obtained.

(2-1) A structure in which the first coil 40C and the second coil 40Dare wound around the core 30 is accommodated in the box body 11, in thisstate, the first coil 40C and the electrode wire members 441 a and 442 aare joined together by welding and the second coil 40D and the electrodewire members 441 b and 442 b are joined together by welding, and the lidbody 12 can be attached to the box body 11.

As described above, by attaching the electrode wire members 441 a, 442a, 441 b, and 442 b to the structure in the state of being accommodatedin the box body 11, it is possible to complete a main portion of thecoil component 1 excluding the lid body 12. Therefore, in the weldingprocess of the third wire members 431 a, 432 a, 431 b, and 432 b andother components and the welding process of the second wire members 42and other components, it is not necessary to change the posture of thebox body 11 and the like. Therefore, it is possible to reduce a timerequired for manufacturing and to simplify an apparatus formanufacturing, thereby reducing cost.

Third Embodiment

Hereinafter, a third embodiment will be described.

In this embodiment, the same constituent members as those in the aboveembodiments are denoted by the same reference signs, and descriptionthereof will be omitted as appropriate. Further, description ofrelationships between the same constituent members will be alsoappropriately omitted.

As shown in FIG. 15 and FIG. 16, a coil component lb includes the core30, a first coil 40E, a second coil 40F, the case 10, and the first tofourth electrode terminals 21 to 24 attached to the case 10. Further,the coil component 1 b includes first to fourth ferrite beads 51 to 54.

As shown in FIGS. 16 and 17, the core 30, the first coil 40E, the secondcoil 40F, and the first to fourth ferrite beads 51 to 54 areaccommodated in the case 10. As shown in FIGS. 16 and 18, the first coil40E and the second coil 40F are wound around the core 30. The first coil40E and the second coil 40F are composed of the plurality of first wiremembers 41 and the plurality of second wire members 42. The first andsecond ferrite beads 51 and 52 are attached to the first coil 40E andthe third and fourth ferrite beads 53 and 54 are attached to the secondcoil 40F.

The first to fourth ferrite beads 51 to 54 are formed in cylindricalshapes. The first to fourth ferrite beads 51 to 54 are made of, forexample, a magnetic material such as nickel-zinc (NiZn) ormanganese-zinc (MnZn).

The first columnar portion 41 a of one first wire member 41 constitutingthe first coil 40E is inserted into each of the first and second ferritebeads 51 and 52 of the first coil 40E. Similarly, the first columnarportion 41 a of one first wire member 41 constituting the second coil40F is inserted into each of the third and fourth ferrite beads 53 and54 of the second coil 40F.

Each of the axial lines of the first to fourth ferrite beads 51 to 54 isparallel to the center axis of the core 30. The first to fourth ferritebeads 51 to 54 are located in the outer side portions in the radialdirection of the core 30. Accordingly, the first to fourth ferrite beads51 to 54 face the outer side surface 30 d of the core 30. In addition,the first to fourth ferrite beads 51 to 54 are positioned at fourcorners of the case 10 in a state of being accommodated in the case 10.

The first ferrite bead 51 is located closer to the first end portion 401a in the first coil 40E. In other words, the first ferrite bead 51 islocated at a position where the first coil 40E is wound substantiallyone turn from the first end portion 401 a. The second ferrite bead 52 islocated closer to the second end portion 402 a in the first coil 40E. Inother words, the second ferrite bead 52 is located at a position wherethe first coil 40E is wound substantially one turn from the second endportion 402 a.

The third ferrite bead 53 is located closer to the first end portion 401b in the second coil 40F. In other words, the third ferrite bead 53 islocated at a position where the second coil 40F is wound substantiallyone turn from the first end portion 401 b. The fourth ferrite bead 54 islocated closer to the second end portion 402 b in the second coil 40F.In other words, the fourth ferrite bead 54 is located at a positionwhere the second coil 40F is wound substantially one turn from thesecond end portion 402 b.

The first to fourth ferrite beads 51 to 54 are arranged around the core30 at the same time as, for example, arrangement of the wire membersaround the core 30. In the step shown in FIG. 7 in the above firstembodiment, the core 30 is mounted. At this time, the first columnarportions 41 a of the first wire members 41 are inserted into the firstto fourth ferrite beads 51 to 54.

Next, noise removal of a normal mode component will be described. Anormal mode current flows, for example, through the first coil 40E inthe direction from the first end portion 401 a toward the second endportion 402 a and through the second coil 40F in the direction from thesecond end portion 402 b toward the first end portion 401 b. When thenormal mode current flows through the first coil 40E, first magneticflux is generated in the core 30 by the first coil 40E. When the normalmode current flows through the second coil 40F, second magnetic flux isgenerated in the core 30 in the direction opposite to the first magneticflux. Since the first magnetic flux and the second magnetic flux in thecore 30 cancel each other, the first coil 40E and the core 30, and thesecond coil 40F and the core 30 do not act as an inductance component.

On the other hand, when the normal mode current flows through the firstcoil 40E, magnetic flux is generated by the first coil 40E in each ofthe first and second ferrite beads 51 and 52. When the normal modecurrent flows through the second coil 40F, magnetic flux is generated bythe second coil 40F in each of the third and fourth ferrite beads 53 and54. Therefore, the first coil 40E and the first and second ferrite beads51 and 52 act as inductance components, and the second coil 40F and thethird and fourth ferrite beads 53 and 54 act as inductance components,thereby removing noise of the normal mode component.

Next, noise removal of a common mode component will be described. Acommon mode current flows, for example, through the first coil 40E inthe direction from the first end portion 401 a toward the second endportion 402 a and through the second coil 40F in the direction from thefirst end portion 401 b toward the second end portion 402 b. When thecommon mode current flows through the first coil 40E, first magneticflux is generated in the core 30 by the first coil 40E. When the commonmode current flows through the second coil 40F, second magnetic flux isgenerated in the core 30 in the same direction as the first magneticflux. Therefore, the first coil 40E and the core 30, and the second coil40F and the core 30 act as inductance components, and noise of thecommon mode component is removed.

As described above, according to the embodiment, in addition to the sameoperational effects as those of the above-described embodiments, thefollowing operational effects can be obtained.

(3-1) Impedance of the normal mode can be increased while maintainingthe impedance of the common mode. The material of the first to fourthferrite beads 51 to 54 can be made different from that of the core 30.Therefore, the degree of freedom in setting of the impedance of thenormal mode is increased.

(3-2) One first wire member 41 constituting the first coil 40E isinserted into each of the first and second ferrite beads 51 and 52 andone first wire member 41 constituting the second coil 40F is insertedinto each of the third and fourth ferrite beads 53 and 54. Thus, thefirst to fourth ferrite beads 51 to 54 can be reduced in size, and thefirst to fourth ferrite beads 51 to 54 can be mounted at desiredpositions.

(3-3) The first to fourth ferrite beads 51 to 54 are located in theouter side portions in the radial direction of the core 30. Accordingly,the degree of freedom of arrangement of the first to fourth ferritebeads 51 to 54 on the core 30 is increased.

(3-4) The first to fourth ferrite beads 51 to 54 are located at the fourcorners of the case 10. Accordingly, the first to fourth ferrite beads51 to 54 can be arranged in dead spaces of the case 10, and the deadspaces can be effectively utilized. As a result, it is possible tosuppress increase in the size of the coil component lb including thefirst to fourth ferrite beads 51 to 54.

Hereinafter, variations on the respective embodiments described abovewill be described. Note that in the description of the joint structurebetween the first wire members 41 and the second wire members 42, onlythe first joining portions 41 d of the first and second joining portions41 d and 41 f of the first wire members 41 are illustrated, but the samestructure can be applied to the second joining portions 41 f.

The shapes of the first wire members and the second wire members may bechanged as appropriate. As shown in FIG. 19A, a through-hole 42 c havinga circular opening is formed in an end portion of each second wiremember 42. An inner diameter of the through-hole 42 c is slightlysmaller than the outer diameter of the first joining portion 41 d ofeach first wire member 41. The first joining portion 41 d of the firstwire member 41 is press-fitted into the through-hole 42 c. In otherwords, the through-hole 42 c and the first joining portion 41 d arejoined together using a tight fitting structure. In this case, the innercircumferential surface of the through-hole 42 c is a joining surfacewhich is fitted with the side surface of the first joining portion 41 d.In addition, the diameter and the like of the through-hole 42 c are setsuch that the area of the inner circumferential surface thereof islarger than the average cross-sectional area of each second wire members42. Thus, by forming the tight fitting structure between thethrough-hole 42 c and the first joining portion 41 d, the innercircumferential surface of the through-hole 42 c and the side surface ofthe first joining portion 41 d can be reliably brought into contact witheach other over the entire circumference. By employing such a tightfitting structure, since the side surface of the first joining portion41 d and the inner circumferential surface of the through-hole 42 c arenot separated from each other, it is hard for each second wire member 42to fall off in the manufacturing process.

Note that in order to join the through-holes 42 c and the first joiningportions 41 d at the tips of the first wire members 41, theabove-described tight fitting structure may not be adopted and the firstjoining portions 41 d at the tips of the first wire members 41 may befitted into the through-holes 42 c without any gap therebetween.

Further, the shapes of the side surfaces of the first joining portions41 d at the tips of the first wire members 41 and the shapes of the endsurfaces 42 a and 42 b of the second wire members 42 may beappropriately changed as long as they can be welded to each other andthe cross sections of the welding portions have areas equal to or largerthan the average cross-sectional area. For example, the shapes may bechanged such that parts thereof make surface contact with each other.

In the first to third embodiments, the tight fitting structure describedabove may be employed for joining the first wire members 41 and thesecond wire members 42. In this case, it is sufficient that thecurvatures (curvatures of the cylindrical surfaces) of the side surfacesof the first joining portions 41 d of the first wire members 41 are madeslightly larger than the curvatures (curvatures of the recessedcylindrical surfaces) of the end surfaces 42 b of the second wiremembers 42 and the side surfaces of the first joining portions 41 d andthe end surfaces 42 b of the second wire members 42 are fitted with eachother.

As shown in FIG. 19B, in the end portions of the second wire members 42,grooves 42 d having, as inner surfaces, recessed cylindrical surfacescorresponding to the first joining portions 41 d of the first wiremembers 41 are formed. The curvatures of the inner surfaces of thegrooves 42 d are equal to the curvatures of the side surfaces of thefirst joining portions 41 d after fitting. The inner surfaces of thegrooves 42 d are joining surfaces which are fitted with the sidesurfaces of the first joining portion 41 d. The curvatures and the likeof the grooves 42 d are set such that the areas of the inner surfacesthereof are larger than the average cross-sectional areas of the secondwire members 42. In addition, the lengths of the inner surfaces(recessed cylindrical surfaces) of the grooves 42 d in thecircumferential direction are equal to the lengths of the halfcircumferences of the side surfaces (cylindrical surfaces) of the firstjoining portions 41 d. Also in this configuration, it is possible toemploy the above-described tight fitting structure.

In the first embodiment, the lengths of the end surfaces 42 b (recessedcylindrical surfaces) of the second wire members 42 in thecircumferential direction are made equal to the lengths of the halfcircumferences of the side surfaces (cylindrical surfaces) of the firstjoining portions 41 d, but the lengths thereof in the circumferentialdirection may be shorter than the lengths of the half circumferences ormay be longer than those in a range of equal to or shorter than thelengths of the whole circumferences. The same applies to therelationship between the inner surfaces of the grooves 42 d and the sidesurfaces of the first joining portions 41 d described in the abovevariation.

As shown in FIG. 19C, the first wire members 41 may be formed by a barmaterial (round material) having a circular cross section. The roundmaterial is easier to obtain and lower in cost than the square material.Accordingly, the cost of the coil component can be reduced.

As shown in FIG. 19D, the first wire members 41 having circular crosssections may be used, and the outer dimensions (diameters) of the firstjoining portions 41 d at the tips of the first wire members 41 may bemade equal to the outer dimensions (diameters) of the first columnarportions 41 a.

In addition, the cross-sectional shapes of the first wire members 41 andthe second wire members 42 may be polygonal shapes other than thecircular and square shapes. In the case where the second wire members 42are formed by the bar material (round material) having the circularcross section, as in the case of the first wire members 41, the cost ofthe coil component can be reduced. Even if the cross-sectional shapes ofthe first wire members 41 and the second wire members 42 are not square,it is possible to obtain an operational effect similar to theoperational effect (1-5) in the first embodiment as long as they arepolygonal shapes.

The shape of the core 30 may be changed as appropriate. For example, itmay be an annular shape such as a polygon, an ellipse, or an oval inplan view. In addition, the shape of the longitudinal cross section ofthe core 30 is not limited to a rectangular shape, and may be apolygonal shape other than the rectangular shape, a circular shape, orthe like. In this case, it is preferable that the first wire members 41and the second wire members 42 have shapes following the outer shape ofthe longitudinal cross section of the core 30.

The coil component may be formed by winding one coil around the core 30or formed by winding equal to or more than three coils around the core30. Although in each of the above embodiments, the first wire members 41are formed by bending the bar material, the first wire members 41 may beformed by another method. For example, the first wire members 41 may beformed by pressing or cutting. Further, at least one of the first andsecond columnar portions 41 a and 41 b and the connecting portion 41 cshown in FIG. 4B may be formed as a separate member, and these may bejoined together by welding or the like to form each first wire member41.

The joint parts of the coils, such as the joint parts between the firstwire members 41 and the second wire members 42, can be joined by otherwelding methods than the laser beam welding described in each of theabove embodiments, such as resistance welding and diffusion welding.

Even if the interfaces, which are easy to be generated in joining ofdifferent types of metals as described above, are generated in the jointparts, it is sufficient that the resistance loss of the coil componentfalls within an allowable value range, and for example, the first wiremembers 41 and the second wire members 42 may be joined together bysolder. In this case, the welding portions are formed by the solder.

Although the first wire members 41 and the second wire members 42 aremade of the same metal material, they can also be made of differentmetal materials. In this case, it is preferable that metals with a smalldifference in physical properties therebetween be selected. For example,when the laser beam welding is used for joining both of the wire members41 and 42, it is preferable that metals with small differences in athermal expansion coefficient, thermal conductivity, and meltingtemperature therebetween be selected, and when the resistance welding isused therefor, it is preferable that metals with small differences inresistivity in addition to the thermal expansion coefficient and thethermal conductivity therebetween be selected.

What is claimed is:
 1. A method of manufacturing a coil component, themethod comprising: arranging first wire members around an annular core;arranging each of second wire members between the first wire membersadjacent to each other in a circumferential direction of the core andbringing joining surfaces of the second wire members into contact withside surfaces of joining portions at tips of the first wire members; andforming a coil wound around the core by the first wire members and thesecond wire members by welding the side surfaces of the joining portionsand the joining surfaces.
 2. The method of manufacturing the coilcomponent according to claim 1, wherein the first wire members and thesecond wire members made of a same metal material are used, and in theforming, the first wire members and the second wire members are joinedtogether by welding portions which are formed by melting the first wiremembers and the second wire members.
 3. The method of manufacturing thecoil component according to claim 1, wherein: the forming includesforming welding portions for joining the side surfaces of the joiningportions and the joining surfaces by emission of laser light; and thewelding portions are formed by the laser light emitted from the samedirection.
 4. The method of manufacturing the coil component accordingto claim 1, wherein in the arranging of each of second wire members, thesecond wire members are respectively fitted into between the first wiremembers adjacent to each other in the circumferential direction of thecore to bring the joining surfaces of the second wire members intocontact with the side surfaces of the joining portions at the tips ofthe first wire members.
 5. The method of manufacturing the coilcomponent according to claim 1, wherein the second wire members havingthe joining surfaces areas which are larger than an averagecross-sectional area of the second wire members are used.
 6. The methodof manufacturing the coil component according to claim 1, wherein: thefirst wire members having step portions formed in the tip portions ofthe first wire members are used; and in the arranging of each of secondwire members, the second wire members are fitted into the first wiremembers so as to abut against the step portions.
 7. The method ofmanufacturing the coil component according to claim 1, wherein: thefirst wire members having the joining portions of cylindrical shapes areused; and the second wire members having the joining surfaces asrecessed cylindrical surfaces which are provided in end portions of thesecond wire members and are fitted with the joining portions are used.8. The method of manufacturing the coil component according to claim 1,wherein: the first wire members having the joining portions ofcylindrical shapes are used; and the second wire members having thejoining surfaces as inner circumferential surfaces of through-holeswhich are provided in the second wire members and into which the joiningportions are tightly fitted are used.
 9. The method of manufacturing thecoil component according to claim 1, wherein wire members havingrectangular cross sections are used as at least one of the first wiremembers and the second wire members.
 10. The method of manufacturing thecoil component according to claim 2, wherein: the forming includesforming the welding portions for joining the side surfaces of thejoining portions and the joining surfaces by emission of laser light;and the welding portions are formed by the laser light emitted from thesame direction.
 11. The method of manufacturing the coil componentaccording to claim 2, wherein in the arranging of each of second wiremembers, the second wire members are respectively fitted into betweenthe first wire members adjacent to each other in the circumferentialdirection of the core to bring the joining surfaces of the second wiremembers into contact with the side surfaces of the joining portions atthe tips of the first wire members.
 12. A coil component comprising: anannular core; and a coil wound around the core, wherein: the coilincludes first wire members and second wire members; the second wiremembers have joining surfaces in contact with side surfaces of joiningportions at tips of the first wire members; and the first wire membersand the second wire members are joined together with welding portionsbetween the side surfaces of the joining portions and the joiningsurfaces interposed therebetween.
 13. The coil component according toclaim 12, wherein areas of the joining surfaces are larger than anaverage cross-sectional area of the second wire members.
 14. The coilcomponent according to claim 12, wherein the first wire members, thesecond wire members, and the welding portions are made of the same metalmaterial.
 15. The coil component according to claim 12, wherein thejoining portions have cylindrical shapes and the joining surfaces arerecessed cylindrical surfaces which are provided in end portions of thesecond wire members and are fitted with the joining portions.
 16. Thecoil component according to claim 12, wherein the joining portions havecylindrical shapes, and the joining surfaces are inner circumferentialsurfaces of through-holes which are provided in the end portions of thesecond wire members and into which the joining portions are tightlyfitted.
 17. The coil component according to claim 12, wherein at leastone of the first wire members and the second wire members have squarecross sections.
 18. The coil component according to claim 12, wherein atleast one of the first wire members and the second wire members havecircular cross sections.
 19. The coil component according to claim 13,wherein the first wire members, the second wire members, and the weldingportions are made of the same metal material.
 20. The coil componentaccording to claim 13, wherein the joining portions have cylindricalshapes and the joining surfaces are recessed cylindrical surfaces whichare provided in end portions of the second wire members and are fittedwith the joining portions.